Many integrated circuit applications require voltages that are higher than the normal power supply voltages. The higher voltages may be used for several purposes, such as for example, programming or erasing cells of an embedded flash memory in an integrated circuit microcontroller. The higher voltage may be generated on the integrated circuit by using a charge pump to boost the normal power supply voltage provided to the integrated circuit. Also, some integrated circuits require that a negative voltage be generated in addition to the normal power supply voltage. A charge pump is typically used to generate the negative voltage. However, implementing a charge pump on the integrated circuit to provide the higher voltage, or the negative voltage, increases the size, complexity, and therefore the cost of the integrated circuit.
Another way to provide the higher voltage is to add a second power supply to the system having the integrated circuit, and simply provide the higher voltage to the integrated circuit via a dedicated pin. However, by requiring a user of the integrated circuit to provide the higher voltage, the number of applications in which the integrated circuit may be used is restricted to system where the second power supply is available.